Motor gasoline containing alkylate of isobutane and thermally cracked naphtha



J. T. KELLY ETAL 2,758,960 MOTOR GASOLINE CONTAINING ALKYLATE OFISOBUTANE Aug. 14, 1956 AND THERMALLY CRACKED NAPHTHA Filed July 9, 1955km @FQQQQRMXEQ N INVENTORS Joe 7. Kelly By 4 Robert J. Lee 7m 1444 E5ATTO/PNFZ United States Patent O MOTOR GASOLINE CONTAINING ALKYLATE OFISOBUTANE AND THERMALLY CRACKED NAPHTHA Joe T. Kelly, Galveston, andRobert J. Lee, La Marque, Tex., assignors, by mesne assignments, to TheAmerican Oil Company, a corporation of Texas Application July 9, 1953,Serial No. 366,9,71 1 Claim. (Cl. 196-150) This invention relates to theproduction of para-ditertiary-butylbenzene. More particularly theinvention relates to the production of p-di-tert-butylbenzene by analkylation process involving benzene, Cs olefins and isobutane. Theinvention also relates to an improved motor gasoline compositioncontaining motor alkylate derived from the alkylation of C6 olefins andisobutane.

In recent years the motor car. manufacturers have striven for increasedhorsepower without increase in engine size. This result has. beenobtained by increasing the compression ratio at which the engineoperates. As a result of this increased compression ratio the octanenumber demand of present-day engines has increased markedly.Furthermore, these engines have introduced a relatively new problem tothe motor gasoline producer. It has been noticed that these highhorsepower, high compression ratio engines have a tendency to knock athigh speed, i. e., under conditions where the engine is operating atsubstantially maximum horsepower output. Previously the point of maximumoctane number demand was in low speed operation, i. e., when the motorcar had just begun to move from standstill.

Low speed octane number demand of motor car engines can be very readilymet by the addition of aromatic hydrocarbons such as benzene or toluene,or by the addition of alkylate. Unfortunately the effective octanenumber of aromatic hydrocarbons principally and of isobutane-butylenealkylate at high speed performance is markedly lower than the efiectiveoctane number at low speed performance. An additional complication isintroduced into the picture by the fact that motor gasoline not onlymust boil over the range of about 100 to about 400 F., but also mustprovide sufiicient volatility for easy starting of the engine and yetnot so much volatility as to incur vapor locking and excessivevaporization losses from the gas tank. Therefore, the requirements ofpresent day high compression motor car engines need a motor gasolinethat is of relatively high efiective octane number throughout theboiling range. The octane number of gasolines is determined by threetests. Two of these tests are laboratory procedures using a standardone-cylinder engine. These tests are known as: F-l which is also knownas the CPR-research method; F-2 which is also known as he CPR-motormethod; the third test uses a motor car under specified operatingconditions on the road; this method is known as the F-27 method. It hasbeen found that the F-2 method octane number is indicative of the highspeed performance of the fuel in a motor gasoline engine; and the F-1method is indicative of the low speed performance. The differencebetween the F-1 number and the F-2 number is known as the sensitivity ofthe gasoline. Low sensitivities are desired.

An object of the invention is the production of p-di-tert-butylbenzene.A specific object of the inven- 2,758,960 Ce P tente Ana- 4,. 1. 56

tion is the recovery of p-di-tert-bntylbenzene from the alkylateproduced in the alkylation of a cracked naphtha boiling in the C6 rangewith isqbutane. Another object is a m r gas n f impr d oct n m er in thhigher boiling portion thereof. Still another object is a motor gasolineof improved octane number sensitivity. Other objects will becomeapparent in. the course of the detailed description of the invention.

It has been found tht p-di-tert butylbenzene is formed when a crackednaphtha boiling in the C6 range and isobutane are contacted under strongacid catalyzed alkyla; tion conditions. The hydrocarbons are separatedfrom the alkylation catalyst and p-d-i-tert-butylbenzene is crystallizedfrom the hydrocarbons; preferably the crystallization is carried out ona heart out obtained by distillation of the total hydrocarbons from thealkylation step.

An improved motor gasoline composition boiling between about and 400 F.is obtained by blending hydrocarbons boiling over the range of about100- and 400 F. and between about 10- and. 25 volume percent, based ongasoline, of a motor alkylate which boils be tween about 185 and 410that has been derived from the strong. acid catalyzed alkylation ofbutane and a k d n phtha b il ng n he Q6 a T rong d aly ed alkylat on prc s u l e in this invention is well known to the art. The strong acidsmay be sulfuric acid, hydrofluoric acid, hydroflutic acid and BFs, or aRF; hydrate. The conditions necessary to obtain optimum yields ofalkylate are set forth in numerous literature articles and patents. Aparticu-. larly good summary of strong acid catalyzed alkylation is setout in Progress and Petroleum Technology.Commercial Alkylation ofIsobutane by A. V. Mrs tik et al., pp. 97-1-08 (Advances in ChemistrySeries No. 5, American Chemical Society). Although certain preferredconditions are described herein, it is intended that the term alkylationconditions shall be construed broadly in light of the knowledge of theart.

The naphtha feed to the alkylation process utilized herein is a crackednaphtha boiling in the C6 range which contains appreciable amounts ofbenzene, i. e., between about and F.; preferably the naphtha feedcomprises a mixture of C6 aliphatic hydrocarbons boiling over the entirerange of about 120 to 185 P. such as is obtained by fractionaldistillation of a wide boiling cracked naphtha. The cracked naphtha maybe ob.- tained from either a thermal cracking operation such as crackingof gas oil or reduced crude, or from a catalytic cracking operation suchas Houdry fixed bed, Houdri flow and TCC moving bed, fluid catalyticcracking, etc.

Thermally cracked naphtha is the preferred feed because of the largerupgrading of the octane number.

The isoparafin used in the alkylation process is isobutane.

Surprisingly, it has been found that sulfuric acid having a strength ofbetween about 85 and 92% produces from thermally cracked naphtha feed amotor alkylate of very low sensitivity as compared with alkylate de-.rived from the alkylation of isobutane and butylene. These particularlydesirable results are obtained when operating under cold acidconditions," i. e., contactor temperatures of bet-ween about 40 and 50F.

The improved motor gasoline composition of the invention containsbetween about 10 and 25 volume percent of the motor alkylate produced inthe alkylation of the cracked naphtha feed and isobutane under strongacid catalyzed alkylation conditions. The motor alkylate ,"a s....."have boils between about 185 and 410 F. Inclusion of the Cs paraflins,which are of relatively low octane nutn- 3 her, is avoided by utilizingthis boiling range. The paraffins are the C6 boiling range materialpresent in the cracked naphtha feed which do not undergo the alkylationreaction, i. e., paraifms, naphthenes and possibly some benzene.

The C7 boiling range cracked naphthas are not a suitable source of motoralkylate for improved sensitivity motor gasoline because of therelatively low efiective octane number of the product and the relativelylow yields of motor alkylate obtainable; and this only at the cost ofenormously higher catalyst consumption.

It has been found that the benzene present in the cracked naphtha feedis alkylated to para-di-tertiarybutylbenzene. This product is found inthe alkylate residue, i. e., the hydrocarbons from the alkylationprocess which boil above about 410 F. The p-di-tert-butylbenzene can berecovered to an appreciable extent from the total hydrocarbons from thealkylation process. However, better yields are obtained by working withthe alkylate residue and preferably with a heart out boiling about theboiling point of p-di-tert-butylbenzene. The high melting point of thep-di-tert-butylbenzene permits the material to be separated from theother hydrocarbons by crystallization at moderate temperatures.Appreciable yields of high purity material may be obtained bycrystallization at temperatures of about 40 F. In general suitableoperating temperatures for the crystallization procedure are betweenabout and 40 F.

The results obtainable from the process of this invention areillustrated by the following experimental data.

The alkylation was carried out in a small continuous fiow unit having aone-gallon capacity reactor section. The particular naphtha feed and theisobutane were passed into the reactor where they were contacted withthe catalyst. Intense agitation was provided in the reactor by means ofan air motor driven paddle stirrer. The reactor was maintained at thedesired temperature of operation by means of a refrigerant circulated ina jacket. The acid-hydrocarbon was continuously withdrawn from thereactor and passed to a settler where the hydrocarbons were separatedfrom the spent catalyst. The product hydrocarbons were separated fromthe ex cess isobutane by distillation. The product hydrocarbons werethen separated by distillation into a fraction boiling in about the samerange as the naphtha feed, a motor alkylate fraction boiling from abovethe maximum boiling temperature of the naphtha feed to about 410 F., andan alkylate residue boiling above about 410 F.

Except as noted otherwise, the ratio of isobutane to olefins present inthe naphtha feed was maintained at between about 79:l. When usingsulfuric acid catalyst the reactor temperature was maintained betweenabout 40 and 50 F., i. e., cold acid conditions. In all runs the ratioof sulfuric acid to hydrocarbon was about 1.3. The reaction time variedbetween about and minutes. Sufiicient pressure was maintained on thesystem to keep the feed and isobutane in the liquid state.

For purposes of comparison runs were made using BFs hydrate catalyst.This catalyst consisted of about 75 weight percent BF3 and the remainderwater.

The octane numbers were obtained according to the F1 and F 2 methods. Adifierential technique was used and duplicate runs were made in order toimprove accuracy. Blends of motor alkylate in a typical premium gasolinebase stock were made and the blending octane number of the motoralkylate was calculated from the octane number of the blend and theoctane number of the base stock.

Various naphtha feeds were tried. For example, the

C5 boiling range fraction of naphtha derived from the thermal crackingof gas oil and from the fluid catalytic cracking of gas oil, also the C7boiling range cracked naphthas of the above types. For purposes ofcomparison an alkylation was carried out utilizing ordinary refinerymixed butylenes as the feed. Still another experiment was made using theparaffins from a thermal Cs naphtha alkylation as the isoparafiins andbutene-2 as the olefin.

In general the C6 boiling range naphthas boil between about 120 and 185F. and the C7 boiling range naphthas boil between about 185 and 216 F. Adetailed inspection of typical thermal Cs naphtha and catalytic Csnaphtha is set out below:

Thermal Catalytic Ct naptha Ca naptha 1 84. 5 94. 3 F-2 72. 9 80. 4Chromatographic analysis:

The base stock used in these experiments was a typical premium gasolineboiling between about 100 and 400 F. This gasoline was a mixture ofaromatics and catalytically cracked naphthas. The octane numbers of thisbase stock were F-l, 91.1 and F-2, 79.6. The sensitivity of this basestock was 11.5.

The results of these tests are presented in Runs A through I set out inTable 1. Runs A, B and C show sulfuric acid catalyzed alkylation of athermal naphtha boiling in the Cs range. Run D shows a BFs hydratecatalyzed alkylation of this thermal Cs naphtha. Runs E and F show theresults of the alkylation of a thermal naphtha boiling in the 01 rangeusing sulfuric acid and BF3 hydrate catalyst, respectively. Run G showsthe results of sulfuric acid catalyzed alkylation of catalyticallycracked naphtha boiling in the C6 range.

The data show that BFs hydrate does not produce as good an octane numberproduct as does sulfuric acid. This product is of entirely acceptablequality.

Runs E and F show that no advantage in terms of F-l octane numberimprovement of the motor alkylate over the naphtha feed is obtained bythe use of thermal cracked naphtha boiling in the C7 range.

Run G shows that in terms of blending octane number (BON) by the F-1method a loss of quality is obtained when catalytically cracked naphthain the Ca boiling range is used as the feed to the alkylation process.

Runs A, B and C show a significant beneficial effect of the use of C6range thermally cracked naphtha feed. Surprisingly these runs show thatwhen using 86% and 91.6% sulfuric acid as the catalyst, the BON-F-1number is as good as the same number for the 98.5 acid run and theBON-F-Z numbers are about three units higher than Run C. Thus the motoralkylate from Runs A and B have a sensitivity very markedly lower thanthe motor alkylate from Run C or from Run G. Thus by the use of C5 rangethermally cracked naphtha feed and sulfuric acid of about 85 to 92%strength, it is possible to produce a motor alkylate of improvedblending octane number in both F-l and F-2 methods and of extremely lowsensitivity.

reases Table 1 Run A B C D E F G H I Naphtha feed I O6 b C; d 04iGi/olefin 7. 3 7. 5 7.1 7. 5 8. 3 8. 6 7. 3 B 4 4. 5 H 804 conc.,percent 1 86 1 91. 6 98. 5 1 91. ,6 H 98-. 5 98. 5 98. 5 Temperatme, "F43 '45 42 77 43 81 43 46 43 Yield, v. percent on olefin:

Parafiins 77. 9 59. s 88.7 107. 5 151. 3 1 40, s Motor alk'ylate 75. 997. 2 100. 3 99. 8 41. 4 62. 8 110 128 161. 2 Alkylate residue 23. 2 17.17. 3 16. 8 31. 9 28. 8 30 31- 9. 8 Octane number date:

N aphtha feed: p

F-l 84; 84. 5 84. 5 84. 5 79. 8 79. 8 94; 3 F-Z 72.9 72.9 72.9 72.9 80.4Motor F- 77; 8 79. 9 81. 7 79; 8 70. 9 68; 4 80. 2 F-2 81. 1 82.0 83. 778. 5 72. 6 69. 0 81. 9 BON F-l. 87. 5 85. 5 87. 5 84. 5 81. 5 78.0 90.0BON F-2 84.- 3 84; 3 81. 5 82. 0 79. 4 77. 0 83. 5 BONA. 3.2 1.2 6.0 2.52.1 1.9 6.5

1 Thermal Ce. 2 Thermal C1. x Obtained from fluid catalytic cracking ofgas 011. b fParaflins from run B. Naphtha feed/butene-2. v g 4 Mixedbutylene's from fluid catalytieally cracking. e BF; hydrate (75% BEE)catalyst. l Partically spent alkylation acid.

Run H shows the results of alkylatmg butene-Z and Table 3 the paraflinsfrom Run B using 98.5% sulfuric acid catalyst. This run shows the markedincrease in octane Run M N 0 numbers of the alkylate as compared withthe paraflin 30 charge obtalfled from Run B. Naphtha Feed. Thermal 0....Thermal 0.. Catalytic o6.

* Qlefins, V61, percent.... 43 41 53 Inspections are presented below onthe motor alkylate and the parafiins obtained in Runs B and. G,respectively:

Run 13 Run G Motor Paraflins Motor Pai-affins alkylate alkylate 79. s62. a s0.- 2 77. 4 82.0 69. 1 81. 9 76. 2

0. 2 Nil 1. 0 Nil Table 2 V. percent Sensi- Run motor F-l F-2 tivityalkylate None 94. 0 82. 8 11. 2 93.0 83,.- 0 10. 0 92. 7 83. 3 9. 4

Para-di-tertiary-butylbenzene was recovered from the alkylate residue inthe runs presented below. The pertinent information on these runs ispresented in Table 3 below:

Yield Percent on Napht a) .Parafiins 47.2. Motor A-llrylate 29 58.0.Alkylate Residue--- 10.5. p'-di-tert-butylhenze1ie Appreciable;

percent on ben- 'zene).

In the above Runs M, N and 0 an initial recovery ofp-di-"tertbutylbehzene was obtained by cooling the alkylate residue toabout 30 F. The crystals formed during the cooling were recovered byfiltration. The crystals were washed with ethyl alcohol to remove anyoil film. In Run 0 no attempt was made to recover all of thep-di-te'rt-butylbenz'cne; therefore, the yield is shown merely asappreciable. In Run M the recovery of p-di-te'r't-bntylbengene wasmaximized by fractionating the mother li uor from the initialcrystallization in an Oldershaw column. A heart out boiling betweenabout 438 and 475 F. (226246 C.), i. e., close boiling about the boilingpoint of p-di-tert-butylbenzene, was taken. This hea'rt cut was cooledto about 30 F. and the crystalline material separated by a filtration.The crystals were washed with alcohol to remove any oil film. Within thelimit of experimental determination the two crystalline products wereidentical. The sum total yield in Run M was 170.5% based onbenzenepresent in the naphtha feed as compared with a theoretical yield of244%. v

The crystalline product had a melting point of 77 C. which wasessentially identical to the melting point of a sample ofp-di-tert-butylbenzeneknown to be 99.9+% pure. The melting point of amixture of the unknown crystalline material and the pure material wasdetermined; the mixed melting point was identical with the melting pointof the individual components, thereby establishing identity of the twomaterials. The carbon-hydrogen analysi's of the unknown material was88.23% carbon and 11.77% hydrogen; this is in close agreement with thetheoretical analysis for di=tertiary-butylbenzene. The identity of theunknown material was further established by a comparison of the infraredspectra of the unknown material and the pure material. These threetechniques 7 conclusively establish the identity of the crystallineproduct from the cooling of the alkylate residue as essentially purepara-di-tertiary-butylbenzene.

The annexed drawing which forms a part of this specification illustratesone embodiment of a process for producing p-di-tert-butylbenzene from acracked naphtha boiling in the C6 range. Variations of this process maybe readily arrived at by those skilled in this art and it is to beunderstood that these modifications are considered to be within thescope of the invention.

In the drawing the feed to the process is a thermally cracked naphthaboiling between 122 and 180 F. which contains about 3% of benzene andabout 50% of olefins. Feed from source 11 is passed by way of line 12into line 13.

Isobutane from source 14 is passed into line 13 where it meets the feed.In this embodiment nine parts of isobutane are present in the reactionzone per part of olefin present in the feed.

The feed contains H28 and mercaptans. These sulfur compounds preferablyare removed prior to contacting the feed with sulfuric acid. In thisembodiment the contents of line 13 are introduced at a lower portion ofvessel 16. Vessel 16 is a vertical cylindrical vessel adapted to provideintimate intermingling of two immiscible liquids. Aqueous caustic fromsource 17 is passed by way of line 18 into an upper part of vessel 16.Herein the aqueous caustic solution is a 20% solution of NaOH in water.Herein volume percent of aqueous caustic solution is used. The aqueouscaustic, feed and isobutane are intermingled in vessel 16. An aqueousphase consisting of water, caustic mercaptides and sodium sulfide iswithdrawn from the bottom of vessel 16 by way of line 19.

Essentially HzS-free-naphtha-isobutane is withdrawn from the upper partof vessel 16 by way of line 21 and is introduced into vessel 22. Vessel22 is similar in construction to vessel 16. Water from source 23 ispassed byway of line 24 into an upper part of vessel 22. The

water removes from the naphtha-isobutane the occluded aqueous causticsolution. Herein about volume percent of water is used. An aqueous phaseis withdrawn from the bottom of vessel 22 by way of line 26.

The washed naphtha-isobutane is withdrawn from vessel 22 and is passedby way of line 28 into heat exchanger 29. In heat exchanger 29 thetemperature of the naphthaisobutane is lowered to about that of thereactor, i. e., about 40 F. The cold stream is passed by way of line 31into reactor 32.

Reactor 32 is shown schematically herein. The reactor may be any form ofvessel such as is conventionally used in this art. In reactor 32 thenaphtha and isobutane are contacted with sulfuric acid having aconcentration of 90%. About 1.5 parts of acid are present per part ofnaphtha-isobutane. The emulsion of isobutane product hydrocarbons andacid is withdrawn from reactor 32 by way of line 34 and is introducedinto acid separator 36.

Acid separator 36 is shown herein as an inclined cylindrical vessel.However, any conventional form of liquid- ]iquid separator may be used.The acid phase is withdrawn from separator 36 by way of line 38 and isrecycled to the reactor by way of line 39. The phase may be withdrawnfrom the system by way of valved line 41. Fresh makeup acid from source43 is passed by way of valved line 44 into line 39.

Although in this illustration 90% fresh sulfuric acid is used, it is tobe understood that motor alkylate of satisfactory octane number qualitymay be obtained by using spent alkylation acid as long as the spent acidhas an effective acid content of at least about 85%.

isobutane and product hydrocarbons are withdrawn from acid separator 36by way of line 46 and are introduced into vessel 47. Vessel 47 issimilar in construction to vessel 16. Aqueous caustic solution fromsource 48 is introduced by way of line 49 into an upper part of vessel47. An aqueous phase is withdrawn from the bottom of vessel 47 by way ofline 51. Substantially neutral isobutane and product hydrocarbons arewithdrawn from vessel 47 by way of line 53 and are introduced intofractionator 54 which is provided with reboiler 56.

In fractionator 54 the unreacted isobutane is withdrawn overhead and isrecycled to the reactor by way of lines 58 and 13.' The debutanizedhydrocarbons are withdrawn from fractionator 54 by way of line 61 andare passed into fractionator 62 which is provided with reboiler 63.

Under the conditions of alkylation described hereinabove, apparentlyonly the C6 olefins and benzene react. The unreacted materials from theCa feedparaflinsare taken overhead from fractionator 62 and are passedto storage not shown by way of line 64. The hydrocarbons boiling aboveabout 185 F. are withdrawn from the bottom of fractionator 62 by way ofline 66.

The total alkylate in line 66 is introduced into fractionator 68 whichis provided with internal heat exchanger 69. In fractionator 68 a motoralkylate fraction boiling between about 185 and 410 F. is taken overheadand is passed to storage by way of line 71. This motor alkylate isblended with premium quality gasoline base stock to produce a motorgasoline of improved octane sensitivity. In this instance 20 volumepercent of motor alkylate is present in the motor gasoline.

Hydrocarbons boiling above about 410-alkylate res idue-are withdrawn asthe bottoms fraction from fractionator 68 by way of line 73. Thealkylate residue is passed into fractionator 76 which is provided withinternal heater 77. In fractionator 76 a heart out of hydrocarbonsboiling closely about the boiling point of p-ditert-butylbenzene isproduced and is withdrawn therefrom by way of line 78. This heart outboils between about 438 and 475 F. Lower boiling hydrocarbons are takenoverhead and are passed to storage not shown by way of line 81. A higherboiling fraction is produced as a bottoms product and is passed tostorage not shown by way of line 82.

The heart out is introduced by way of line 78 into chiller 84. Chiller84 is schematically represented herein and may be any conventional formof cooler which permits the formation of crystals therein. In thisembodiment the temperature of the heart out is reduced to about 15 F. inchiller 84. The chilled oil-crystal mixture is introduced by way of line86 into crystallizer 87.

Crystallizer 87 may be any form of conventional appa ratus permittingseparation of crystals from a mother liquor. Herein a crystallizer isschematically illustrated which permits Withdrawal of substantiallyoil-free crystals. Mother liquor is withdrawn from crystallizer 87 byway of line 88. The mother liquor may be given further treatment if theabsolute maximum yield of the p-di-tertbutylbenzene is desired. Productp-di-tert-butylbenzene is withdrawn from crystallizer 87 by way of line89.

If essentially pure crystalline material is desired the product fromline 39 may be given further treatment to remove occluded oil.

Thus having described the invention, what is claimed is:

A motor gasoline of improved octane in the higher boiling range whichcontains between about 10 and 25 volume percent of a motor alkylateboiling between about 185 and 410 F. that has been obtained by the coldacid alkylation of isobutane and a thermally cracked naphtha boilingover the range of about and F. using sulfuricacid of a strength betweenabout 85 and 92% as the alkylation catalyst.

References Cited in the file of this patent UNITED STATES PATENTS2,421,331 Johnson May 27, 1947 2,433,020 Becker Dec. 23, 1947 2,579,421Egan Dec. 18, 1951 2,653,980 Condon Sept. 29, 1953 2,659,761 Frevel etal Nov. 17, 1953 2,665,316 Bennett Jan. 5, 1954

